Restructure scripts into dev/ and prod/ for the devcontainer

- scripts/prod: entrypoint, db-setup and schema.sql shipped in the image
- scripts/dev: seed/clear db, psql and cleanup, run natively in the
  devcontainer instead of via docker-compose
- move setup.cfg to the repo root so linters pick it up
- Makefile targets run directly in the devcontainer

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/dev/clear-db.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+
+set -e
+
+PGPASSWORD="$PGSQL_PASSWORD" psql -v ON_ERROR_STOP=1 -h "$PGSQL_HOST" -p "$PGSQL_PORT" -U "$PGSQL_USER" -d "$PGSQL_NAME" \
+    -c "DROP SCHEMA public CASCADE; CREATE SCHEMA public;"